Aircraft: B757
Phase of flight: Parked
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown

This report concerns the omission of a potentially significant maintenance log item from the pilot's flight planning maintenance review papers. Because I was the author of the original write-up about a week before; I was aware of its existence. Seeing that we were assigned the same aircraft for this day's flight I informed the Captain the aircraft had had two items that prevented us from flying it the week prior. One item was the failure of the right system hydraulic pressure low light to come on when it should (when system not pressurized). The more significant item; in my opinion; was finding the galley Circuit Breaker (CB) on the cockpit overhead panel popped. When we pulled the flight papers at the airport; this last item (the popped CB) was missing from the log history. Although the log history reflected other items going back [well prior to my first write-up] this item was missing. Some history from the earlier fight. As I boarded the aircraft the flight attendants notified me that the entire aft galley lacked power. Entering the cockpit; I noticed the galley CB on the overhead panel popped. I notified Maintenance; and made a write-up. Maintenance attempted a reset of the CB; and it immediately popped. Hours later; the only way the CB would stay in was if the mechanics removed all power from the aft galley (via pulling CB's in the galley and in the EE compartment). They could not otherwise isolate the source of the electrical problem. More extensive investigation was required. That; coupled with the inability to get the hydraulic pressure light to come on; meant the airplane was grounded. We were assigned another aircraft to fly.After completing that flight I went to the office and pulled up the aircraft history on our dated computer system. Under our standard maintenance review code I found my original write-up; with the corrective action noted (maintenance replaced ELCU per [Maintenance Manual] Ops Checked Normal.) I further noticed another galley write up from several days earlier. The mid galley oven was written up as 'Oven running with door open and produced a lot of heat.' The repair stated 'Replaced oven.' I do recall seeing that in the log history when we operated the flight. But there was a further maintenance history item dated the same day that I am fairly certain did not show up in the pilot's papers: 'Wall bordering mid galley oven is charred.' This is a write-up I hope I would remember. Again; I am fairly certain it wasn't in the history provided the pilots. I am left to surmise that when the mid-galley oven was replaced; the charred wall was discovered. This item seems to be of a piece with the galley oven write up; and I believe should have shown up in the pilots' version of the log history. With the [implementation of the] electronic logbook; pilots must now rely on the log history printout supplied with the flight papers to ascertain [their aircraft's] maintenance history. There is another way to check the history; however; and that is through our [dated computers] in flight offices. Most pilots no longer use these as the software is being phased out; and is virtually useless anymore. But; it still has maintenance functions; a blessing really; if you want to avail yourself of them. The ONLY way I could verify this missing write-up was to conduct a search on this Jurassic system. I certainly hope the company does not remove this tool from the pilots' domain.I called Maintenance Control about the omission. The Controller looked up the history and found the CB write-up. When I told him it was missing from the pilot's [flight planning] version of the log history; he could not explain it (but confirmed it should be there.) I have heard anecdotes from other pilots complaining that known maintenance items were sometimes missing in the flight plan log history. This is the first time I could verify it myself. I have lost some measure of faith in the integrity of the data supplied the pilots. How can a log history show pilots every stuck; now fixed; window shade and every stuck; now fixed; reading lamp; but drop an electrical defect that could result in a fire? How can a significant item escape pilot review simply because a mechanic found it and repaired it? Does the pilot care by whom it was found? Or; does the pilot want to know the entire; recent; history of the airplane; so trends can be spotted; and potential trouble spots noted? Information is power. Pilots share unusual cabin histories with their co-workers. When something odd happens in-flight; knowing what went on before can often inform the crew's response. If the flight attendant in the galley notices a burning smell; rather than dismiss it as an overheated food wrapping or crumbs left behind; perhaps knowing there was a serious issue with the galley/oven previously would lead the crew to remove all power to that oven.As an aside; there is an 'unable to operate' section of the log history. I did not realize until now that unable to operate remarks would only be entered for pilot refusals based on maintenance status. If the pilot makes a log entry and maintenance removes the airplane from service; to correct that non-deferrable defect; no unable to operate entry is made. If the airplane truly is unable to operate; I think it should be noted in the flight papers; regardless of who made that determination. A comprehensive report from a B757 First Officer describing incomplete maintenance data provided to the flight crew regarding a potentially hazardous condition with which the reporter had first hand knowledge from a week previous flight on the same aircraft.